YMU757B Datasheet, PDF (24/43 Pages) YAMAHA CORPORATION – MA-1C

YMU757B
Resetting
This LSI can be initialized by setting the /RST terminal to "L" or through the software as the CLR bit is provided for the
$32h setting.
The inside of the LSI is initialized by doing hardware resetting, and it becomes default condition.
It is completely initialized by software resetting except for the timbre data register of Index10h - 2Fh.
The FIFO data counter will be cleared and FIFO will be empty by initialize.
It is necessary to input CLK_I during resetting. Make sure to input CLK_I for at least 100 clocks during resetting.
After resetting is cancelled, wait for at least 64 clocks of CLK_I input and then start making an access to registers.
Settings and procedure to generate melody
Follow the steps as described below/
1. Set the CLKSEL ($33h) according to the clock frequency inputted for CLK_I.
2. Cancel the power-down mode of the analog section. (Refer to "Resetting sequence of analog section".)
3. Set the timbre data ($10-2Fh), timbre allotment data ($30h), tempo data ($31h) and volumes ($35-37h) as desired.
4. Enter 32 musical score data ($00h) until FIFO is full.
5. Set the IRQ point value of $34h. (Default at the center of FIFO).
6. Set "1" for IRQE of $34h
7.Set "1" for the ST bit of $32h and start the melody.
Setting of clock frequency
The establishment of clock frequency supports two forms of 'preset mode' and 'programmable mode'.
Preset mode: Select clock from 2.688 / 8.4 / 12.6 / 14.4 /19.2 / 19.68 / 19.8 / 27.82 MHz.
Programmable mode: Set to optional frequency from 2.685MHz to 27.853MHz at 55.93kHz intervals.
1)Using preset mode
The establishment of clock frequency can be done by establishing value in $33h with preset mode.
In this case, set “000000000b” to $39h. If set value except for it, movement of LSI isn’t guaranteed.
When value isn't established in either of $33h and $39h(default condition), becomes the condition that 2.688MHz is
set with preset mode.
2)Using programmable mode
The establishment of clock frequency can be done by establishing value in $39h with programmable mode.
In this case, set “000b” to $33h. If set value except for it, movement of LSI isn’t guaranteed.
The value can be set to $39h are “000000000b", from "000110000b" to "111110010b".
If set value except for it, movement of LSI isn’t guaranteed.
-24-